This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. High field MRI systems have the potential to enable ultra high spatial resolution imaging, provide enhanced susceptibility contrast and improved chemical species discrimination in spectroscopy. However high field MRI also poses challenges in the form of decreased radio frequency (RF) excitation homogeneity. This manifests as shading artifacts in the images, making quantitative imaging challenging. Recent developments in multi-transmit radiofrequency pulse design offer a possibility of combating this by using multiple parallel transmitters to excite a complex pattern in excitation k-space using RF and gradient pulses in multiple channels that results in a net uniform excitation field across the region of interest. One of the key inputs to such an RF pulse design is the so-called B1 map, a spatial mapping of the excitation field, which is a time consuming step. Accurate but fast B1 mapping is hence key in generating shading-free images at high fields. To read about other projects ongoing at the Lucas Center, please visit http://rsl.stanford.edu/ (Lucas Annual Report and ISMRM 2011 Abstracts)